A conventional signal transmission system according to DVI (Digital Visual Interface) standard will be described with reference to FIG. 26. FIG. 26 is a diagram illustrating a structure of the conventional transmission system.
In this figure, numerals 2601 to 2603 denote TMDS encoders/serializers provided at the transmitting end, which TMDS-encode inputted component signals such as RED, GREEN, and BLUE signals, serialize the encoded signals, and output the same to transmission lines. Numerals 2604 to 2606 denote TMDS decoders/recoverer provided at the receiving end, which TMDS-decode the received signals, recover the decoded signals, and restore the component signals.
A DE (Data Enable) signal is a signal indicating a period during which the component signal such as RED, GREEN, and BLUE signals exists, and this is a HIGH active signal. For example, the DE signal is LOW in a period of a horizontal synchronizing signal or vertical synchronizing signal of video.
CTL (Control) signals CTL 0, CTL 1, CTL 2, and CTL 3 are prepared as control signals. However, these signals are not in use in the present DVI standard. More specifically, the levels of the signals are always 0.
The so-configured conventional signal transmission system will be described.
The TMDS encoders/serializers 2601 to 2603 at the transmitting end convert video signals (RGB signals) inputted at 8 bits into signals of 10 bits, serialize the converted signals, and output them to transmission lines. The object of the 8 bit-to-10 bit conversion is to reduce data changing points and convert the data into a format that is suitable for high-speed transmission. Further, the TMDS encoders/serializers 2601 to 2603 convert the 2 bit-CTL signals into 10 bit-CTL signals and transmit the converted CTL signals to the transmission lines. The DE signals are also encoded, serialized, and transmitted to the transmission lines.
The TMDS decoders/recoverers 2604 to 2606 at the receiving end decode 10-bit serial data received through the transmission lines into the 8-bit color signals, the DE signals, and the 2-bit CTL signals to decompress the signals.
However, the DVI standard is a standard for transmitting only video signals, and the conventional signal transmission system cannot transmit audio signals.
The present invention is made to solve the above-mentioned problem and has for its object to provide a signal transmitter and a signal receiver that can realize a signal transmission system according to the DVI standard in which audio signals as well as video signals can be transmitted.